Scratch space is space on the
hard disk drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnet ...
that is dedicated for storage of temporary user data.
It is unreliable by intention and has no
back up
In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is " back up", ...
. Scratch disks may occasionally be set to erase all data at regular intervals so that the disk space is left free for future use. The management of scratch disk space is typically dynamic, occurring when needed. Its advantage is that it is faster than e.g. network filesystems.
Scratch space is commonly used in scientific computing workstations, and in
graphic design
Graphic design is a profession, academic discipline and applied art whose activity consists in projecting visual communications intended to transmit specific messages to social groups, with specific objectives. Graphic design is an interdiscipli ...
programs such as
Adobe Photoshop
Adobe Photoshop is a raster graphics editor developed and published by Adobe Inc. for Microsoft Windows, Windows and macOS. It was originally created in 1988 by Thomas Knoll, Thomas and John Knoll. Since then, the software has become the indu ...
. It is used when programs need to use more data than can be stored in system
RAM. A common error in that program is "scratch disks full", which occurs when one has the scratch disks configured to be on the boot drive. Many computer users gradually fill up their primary hard drive with permanent data, slowly reducing the amount of space the scratch disk may take up.
Partitioning off a significant fraction of the boot hard drive and leaving that space empty will ensure a reliable scratch disk. Hard drive space, on a per-gigabyte basis, is far cheaper than RAM, though performs far slower. Though dedicating a separate physical drive from the main operating system and software can improve performance, a scratch disk will not match RAM for speed.
See also
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Scratch tape
In data processing, a scratch tape is a magnetic tape that is used for temporary storage and can be reused or erased after the completion of a job or processing run. During the early years of computing, when magnetic tape was the primary form of ...
*
Swap partition
In computer operating systems, memory paging is a memory management scheme by which a computer stores and retrieves data from secondary storage for use in main memory. In this scheme, the operating system retrieves data from secondary stora ...
*
Temporary folder
In computing, a temporary folder or temporary directory is a directory used to hold temporary files. Many operating systems and some software automatically delete the contents of this directory at bootup or at regular intervals, leaving the direct ...
*
TMPDIR
TMPDIR is the canonical environment variable in Unix and POSIX that should be used to specify a temporary directory for scratch space. Most Unix programs will honor this setting and use its value to denote the scratch area for temporary files ins ...
References
{{DEFAULTSORT:Scratch Space
Computing terminology
Computer files
Rotating disc computer storage media